question

Hi. Your installer may have a good point. At best, on a boat you end up with an 'average' of flat panels, no optimum tilt. Shading from sails, spars, rigging wires, handrails, antennas, etc. will all impinge severely too (yes, even wires). Not to mention clouds.

Then your batt type and capacity comes into it too. You don't say, but let's go Pb's and 200Ah @ 12V. Many will recommend 0.1C to 0.2C, that translates to 20 - 40A. And in practice 30A would likely be rarely needed, but in that instance would be a fair choice.

So it *depends*. The Victron range: https://www.victronenergy.com/upload/documents/Datasheet-BlueSolar-and-SmartSolar-charge-controller-overview-EN.pdf

You could step up to a 100/50, likely at little extra cost, but the 150/ models are unnecessary for you.

If you have more specific info on your setup, please advise..

So with 620 watts wired the PV in 24-36 volts I doubt you are anywhere close to the rated 30 amp max charge output. Have you calculated this? Don't spend the extra money on the 100/50. You can send me cash if you like wasting money.

If you plan to increase your PV down the road, well then it may make sense to bump up to the next size.

Yeh, your larger batts would perhaps tilt me towards the 100/50. But that's just me, I tend to oversize. You're the Cap'n though, and guess the one paying.

Another of those panels (now or later) would be nice then too. Where does one stop, hey?

If your shade is usually substantially different on each panel, you could also consider one mppt per panel, say a 100/20 on each for a good match.

Have fun choosing..